Although large numbers of individuals seek treatment specifically for a principal problem of marijuana dependence, little is known about effective strategies to treat this population. Young adult marijuana users who have been referred by the court system for treatment are characterized by poor retention and outcome in standard outpatient approaches. Targeting this population and addressing their low level of motivation and facilitating treatment engagement may be an effective strategy for early intervention with a population at risk for progression to more severe drug use and associated legal problems. Motivational Enhancement Therapy, directed to fostering motivation for change in this highly ambivalent group, and Contingency Management, directed to foster treatment retention and abstinence, are promising strategies, given their high level of empirical support in other substance-abusing populations and their suitability of the population targeted here. In this study 150 young adults referred by their probation officers for evaluation and treatment of marijuana use will be randomly assigned, using randomization, one of four conditions: (1) standard psychoeducational drug counseling, (2) contingency management plus drug counseling, (3) Motivational Enhancement Therapy (MET), and (4) Contingency Management plus MET. Primary outcomes will be retention in treatment, reduction in marijuana use, and induction to long-term treatment. Study treatments will last 8 we4eks and will be delivered to subjects on an individual basis. Follow-ups at 1,3,6,9 and 12 months after cessation of study treatment will assess the durability and/or delayed emergence of treatment effects.